Browsing by Author "Sharifi, MB"

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    item: Thesis-Full-text
    Calibration and verfication of a-two parameter monthly water balance model and its application potential for evaluation of water resources -a case study of kalu and mahaweli rivers of sri lanka
    Sharifi, MB; Wijesekera, NTS
    Water balance is a method by which we can account for the hydrological cycle of a specific area, with the emphasis on plants and soil moisture. One of the main purposes of a water balance study is to evaluate the net available water resources, both on the surface and in the subsurface. Understanding the behavior of a catchment from a hydrological point of view is necessary when planning and activities needed to be done in the watershed. A-two parameter monthly water balance model for two basins was calibrated and verified using 30 years monthly rainfall, observedflow and pan evaporation data. Kalu Ganga at Ellagawa and Mahaweli Ganga at Morape were selected to estimate the streamflow. The model was calibrated and verified and a good performance was shown for both catchments. The C coefficient for Kalu Ganga at Ellagawa and Mahaweli Ganga at Morape were found as 1 and 1.1 respectively while the SC parameter was found as 800 and 1200 respectively. The MRAE value for calibration period for Kalu Ganga at Ellagawa and Mahaweli Ganga at Morape showed a very good fitting with value of 0.145 and 0.152 respectively. The same for verification period was also very good with value of 0.153 and 0.157 respectively. During the calibration and verification periods value of the Nash–Sutcliffe efficiency for Kalu Ganga at Ellagawa was found as a 93.6% and 92.4% respectively. 93.6% and 94.1% were the Nash–Sutcliffe values for Mahaweli Ganga at Morape respectively. The two parameter monthly water balance model produced a better fitting of MRAE in annual and seasonal values when compared with monthly time series. The two-parameter monthly water balance model with the simple structure and two parameters proved as a very efficient model when simulating the monthly, seasonal and annual runoff. Due to its simplicity and high efficiency in performance, this two-parameter monthly water balance model can be easily and efficiently used for the water resources planning and management.
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    item: Conference-Full-text
    Possibility of Increasing the Land and Water Productivity of Command Area in Labunoruwa Irrigation Tank, Anuradapura, Sri Lanka
    Sharifi, MB; Wijesekera, NTS
    In Sri Lanka, farmers prefer to grow paddy because it is their staple food. The most common reason given for the shortfall is the lack of sufficient irrigation water to rescue crop when the rainfall is lean. The lack of irrigation water is dependant of two aspects. One is the lack of storage and the other is the poor water management. Out of the two, the latter is considered very important because it is an activity that can be easily influenced from the first day of recognition. Therefore, the aim of this study is to carry out a systematic case study application demonstrating the potential to investigate the possibility of increasing land and water productivity through the management of crop types (Paddy, green gram, soya bean and cowpea) grown in each season. Irrigation department guidelines were used for computation of irrigation demand, evapotranspiration requirements and selection of the value of crop growth stages, crop factors and land preparation for Maha season and Yala season with 105 days and 135 days duration for paddy and OFC respectively. Land preparation water requirement, farm loss and the project efficiency were assumed as uniform inputs for all spatial units. Reservoir water balance model based on Irrigation Department guideline was applied to determine the smallest capacity of reservoir that would be required for cultivation of the largest required irrigable area for a pre-determined cropping pattern and intensity for both seasons. After computation of irrigation demand and reservoir water balance modeling, it was found that in all four options, full command area (100%) could be cultivated while in Yala season this result differs as follows. In option 1, paddy was considered for 16% of the command area, while in option 2 this cultivation could be as 10 % of the command area paddy and 28% of the command area green gram. In option 3 and option 4, the cultivable areas were found as 10% for paddy along with 19% for soya beans and 10% for paddy along with 21% for cowpea respectively. Consequently, the second option in which 10 % of the command area was considered for paddy and 28% of the command area for Green Gram was found as a best option to be practiced under Labunoruwa Irrigation Tank in order to increase the water productivity.